1. Field of the Invention
The present invention relates to a high-power zoom lens, which has a zoom ratio of about 24 to 34 times and which can be used in a video camera, an electronic still camera, etc., and particularly relates to a miniaturized high-power zoom lens, which can be used suitably for a surveillance video camera.
2. Description of Related Art
For example, as a zoom lens heretofore used in a video camera, an electronic still camera, etc., there is known a four-group system zoom lens in which a first group and a third group are set as fixed groups, and a second group is moved along an optical axis so as to perform zooming, while the fluctuation of the imaging position caused by the zooming is compensated by moving the fourth group along the optical axis. Japanese Patent No. 3601733 discloses a configuration in which a fifth group is added as another fixed group in order to obtain a zoom lens having a wider angle and a higher zoom ratio than such a four-group system zoom lens.
The configuration disclosed in Japanese Patent No. 3601733 can obtain a high-power zoom lens having a zoom ratio of about 18 to 20 times. In recent years, however, there has grown a request for a miniaturized surveillance zoom lens which has higher optical performance supporting a higher pixel-density camera and which has a zoom ratio of about 24 to 34 times high enough to cover a wider imaging range. In order to increase the power to about 24 to 34 times in the aforementioned four-group system zoom lens, the axial chromatic aberration and the spherical aberration caused by the first group and increasing in the telephoto end has to be suppressed. In addition, the moving distances of the movable groups increasing with the increasing power have to be suppressed to be as small as possible, while the amount of aberrations is suppressed. It has been desired to develop a four-group system zoom lens satisfying these requests.